Main research contents
Sedimentary petrology developed in the early 19th century. The early study of sedimentary petrology was limited to the description and identification of rocks as one of the bases for stratigraphic division and correlation. Over the past two decades, its research content has made tremendous progress, mainly in the following aspects.
(1) To study comprehensively the material composition, structure, structure, classification and nomenclature of sedimentary rocks, as well as the contact relationship between rock occurrence and strata, so as to provide a basis for elucidating the genesis and distribution of sedimentary rocks.
(2) Discuss the formation mechanism of sedimentary rocks, including weathering, transporting, sedimentation and post-sedimentary changes. In particular, the formation mechanism, enrichment and storage of sedimentary minerals (including oil and natural gas in organic combustible minerals) should be studied.
(3) Analyzing the Paleo-sedimentary conditions and restoring the Paleo-sedimentary environment. Based on the comprehensive analysis of various sedimentary facies markers and their spatial and temporal distribution characteristics in sedimentary rocks, the paleoclimatic conditions, paleogeographic conditions, paleomedia conditions and geotectonic conditions during the formation of sedimentary rocks are restored.
(4) To study the basic characteristics and sedimentary conditions of sedimentary rocks in an all-round way and establish sedimentary facies models so as to provide sedimentary geological basis for stratigraphy, sequence stratigraphy, palaeogeography, geochemistry, deposit geology, reservoir geology and petroleum geology, and constantly provide new scientific basis and information for mineral resources survey and exploration. In addition, the relationship between the formation and evolution of sedimentary rocks and geological hazards is also studied, and the related natural disasters are predicted scientifically.
The study of sedimentary rocks includes field geology, geology and Geophysics of overburden areas, and laboratory analysis and laboratory tests.
Field geological observation and description are the basis of studying sedimentary rocks. In field work, lithology of sedimentary rocks can be preliminarily identified, primary sedimentary structures can be described, occurrence and thickness of rocks can be measured, and contact relationship between rocks and their genetic markers can be determined. Based on the comprehensive analysis of the geological phenomena observed in the field, the corresponding field geological maps are compiled, the sedimentary sequence of sedimentary rocks is established, the formation conditions and genetic environment of sedimentary rocks are analyzed, and the ore-bearing property of sedimentary rocks is preliminarily judged.
In the study of sedimentary rocks in the overburden area, the most direct means is to observe and describe the core of sedimentary rocks. We should make full use of the core data to make a scientific judgment on the sedimentary types of key wells. Due to the limited number of drilling cores, it is necessary to make full use of various logging, logging and seismic data to carry out lithological, electrical, physical and petroleum analysis, to conduct a comprehensive study of sedimentary facies markers, logging facies markers and seismic facies markers, to use sequence stratigraphy theory to determine sedimentary sequence, to establish isochronal stratigraphic framework between different wells, and to restore different sedimentary periods of sedimentary basins. The sedimentary features of the deposits indicate the types of sedimentary systems and their spatial distribution. The commonly used logging curves are natural potential, natural gamma ray and microelectrode, induction, density, acoustic wave, formation dip and imaging logging. Seismic data commonly used are mainly two-dimensional and three-dimensional seismic reflection profiles that can reflect the characteristics of sedimentary systems.
Laboratory conventional studies focusing on oil and gas exploration and development mainly focus on thin-section identification, supplemented by some conventional analysis, such as casting thin-section analysis, particle size analysis and physical properties analysis; for different rock types and research purposes, further use of scanning electron microscopy, electron probe and energy spectrum, X-ray diffraction, cathodoluminescence, micro-fluorescence, image analysis, inclusion analysis, etc. Organic geochemical index analysis and stable isotope analysis of clay minerals and carbon, oxygen, sulfur, etc. Based on the above laboratory analysis and laboratory data, the petrological characteristics of sedimentary rocks are comprehensively studied, and the sedimentary environment of Shaanxi-Fujian is inferred. At the same time, it can be used to evaluate the source rock and reservoir.
Since the 1960s, in view of the actual needs of oil and gas exploration in the world, modern sedimentary investigation and indoor flume simulation experiments have been extensively carried out. Since 1990s, large-scale water tank simulation experimental devices have been set up for river, delta, lake and gravity flow sedimentary systems. In addition to flume physical simulation experiments, numerical simulation and sediment diagenesis simulation experiments have also been carried out. These experimental simulations attempt to reproduce the whole process of sediment and sedimentary rock formation from both forward and inversion ways, and provide qualitative and quantitative scientific basis for retrospecting the formation and metallogenic regularity of sedimentary rock.